Electric furnace



R. A. nmscou. ELECTRIC FURNACE.

APPLICATION HLED DEC-5, 1919. BEHEWED NOV- l. I921.

Patented June 27, 1922.

I INVENTOR @zz'sco/f A TTORNE Y8 WITNESSES SSS/1% citizen of the UnitedStates, and aresident PATENT orrlce.

ROY A. DRISCOLIJ, OF GREAT FALLS, MONTANA.

nnnornro romance.

Specification of Letters Patent.

Patented June 2'7, 1922.

Application filed December 5, 1919, Serial No. 342,680. Renewed November1, 1921. Serial No. 512,107.

To aZl w homi't may comm m:

Be it known that I, Box A. DRISCOLL, a

of Great Falls, county of Cascade, State of Montana, have invented a newand Improved Electric Furnace, of which the following is a full, clear,and exact description This inventionrelates to electric furnaces, andhas reference more particularly to an electric furnace in which the ore,slagging materials, and fuel is charged into the furnace by means of arotary tube through which the waste gases from the furnace pass.

An object of this invention is to'prov-ide an electric furnacecombiningthe advan' tages inherent in ordinary electric furnaces with theadvantages common to blast furnaces of providing a heated chamberthrough which the ore-slagging materials-fuel mixture passes beforeentering.

. said furnace, where a partial reduction of the ore takes place.

Another object of this invention is to provide. an electric furnace inwhich very low grade. fuel such. as slack, oil residue, etc.,

- may be utilized.

A further object of this invention is to provide a highly efficientelectric furnace which will be.charged automatically, so that laborcosts are greatly reduced.

A still further object of this invention is to provide an electricfurnace in which a charge is thoroughly mixed, preheated, and

partially reduced by the waste gases issuing from the furnace beforesaid charge enters said furnace. f

A' still further object of the invention is to provide an electricfurnace in which all the operations are continuous so that a uni formproduct is obtained.

It is a, well known fact that the blast furnace is a very efiicientmeans for the reduclarge areas of the western part of the United States,and in other sections of the world, enormous quantities of water powerare available in a region where iron ore and cheap carbon in the form oflow grade coal is also plentiful. In these regions often the coal is notof the type suitable for the manufacture of coke, so that theoperation'of a blast furnace is a commercial impossibility, since itdepends upon the use of ahigh quality coke or anthracite coal. In theseregions an electric furnace which can utilize the large amount of waterpower available, and

cation in which it is understood that the drawing is merely illustrativeof one example of my electric furnace, which is ada ted to meet theabove requirements, and in w ich the figure is a.perspective view of myimproved electric furnace, "showin parts broken away to disclose theinter1or construction.

Referring to the accompanying drawing by numerals, 10 indicates theoutside shell forming the walls of an electric furnace which is linedwith any refractory material '11, and is provided with a hearth 12composed of any suitable material which jmay be acid, neutral, or basic.is constructed with a roof 13, preferably' frusto-conical in shape, saidroof being also lined with refractory material such as fire brick. Aplurality of electrodes 14, prefer-- ably three in number, extend throuh the roof 13 into the interior of the electric furnace. Theseelectrodes may be formed from sticks of carbon and may be adjustableaxially by means of control wheels 15, so that said electrodes may be'incontact with the charge to form a resistance furnace or may be withdrawnsomewhat, from the charge so that the furnace is operated as acombination resistance and are furnace. The furnace may also be operatedas an arc, induction or a combination of any of the aforementioned typesof furnaces. Furthermore. I do not wish to limit myself to anyparticular type of electric furnace or electric current suppliedthereto, since a direct current or an alternating current operating on asingle, double, or poly-phase circuit may be used. 0

The electrodes 14 may. be supported in the roof 13 of the furnace bymeans of castings 16 having passage 17 through which a liquid may becirculatedto prevent said castings from melting. The electric furnace isalso provided with a transparent door 18 through The said furnace whichthe condition and quality of the charge may be observed. Around the topof the furnace a platform 19 may be fixed, guarded by a rail 20 so thata workman may operate the control wheels 15. Extending through the wall10 of the furnace, I provide a tube 21 in which is rotatably andco-axially mounted a screw conveyor 22, said conveyor passing throughthe bottom of *a storage tank 23, which may preferably contain apowdered fuel so that said fuel may be suplied to the furnace as saidscrew conveyor 15 rotated by any ower means such as a pul ley 24 fixedto said screw conveyor and operatively connected by means of a belt 25to a power shaft 26. The roof 13 in the furnace terminates in anopening, and is connected to a pipe 27 which is bent at right angles soas to rotatably telescope around a rotary reduction furnace 28.

This rotary reduction furnace consists of an outer shell 29 lined withsome refractory material 30, and is rotatably mounted by means of aplurality of encircling bearing rin s 31 fixed to the outside peripheryof the she I 29, said rings resting on supporting rollers 32. Therollers 32 may be journaled in any suitablebearing 33, which rest on aframe work 34. The pipe 27 may be water.

cooled at its junction with the furnace 28 by passing a cooling liquidthrough the chambers 35. The rotary furnace 28 may be rotated by meansof spur gears 36 which are fixed to the outside periphery of the shell29 and engage similar spur gears37 which are fixed to the power shaft26. The power shaft 26 may be rotated bya suitable source of power suchas an electric motor 38 connected by a belt 39 to a pulley 40 which isfixed to the shaft 26. The rotary furnace 28- has its axis preferablyinclined at a slight angle with the horizontal so that material feeds inat its upper end, and gradually works down as the furnace is rotated anddrops into'the electric furnace. The upper end of the rotary furnace 28terminates in a stack 41, which rests on suitable supporting beams 42.

The stack 41 serves to carry away the waste gases issuing from thefurnace 28.v

nace are charged with ore, slagging materials, and fuel by means of ascrew conveyor 43, co-axially mounted in a tube 44, said tube passingthrough the bottom of the stack 41 and telescoping inside the upper'endof the furnace 28. The screw conveyor 43 passes through the bottom of astorage tank 45 which is charged with a mixture of, materials by somesuitable means not shown, and rests on suitable supporting beams 46. Thescrew conveyor 43 may be rotated by any power means such as a motor 47connected by a belt 48 to a pulley 49 fixed to the conveyor shaft- 50 ofthe conveyor .43. Compressed air is supplied to the furnace-through anair duct The rotary furnace 28 and the electric fur-' 51 which isconnected with tuyeres 52 formed in the pipe 27;

In operation, the rotary furnace 28 and screw conveyor 43 arecontinuously rotated so that a steady stream of charging material dropsinto the electric furnace from the lower end of the rotary furnace 28through the pipe 27. Anauxiliary supply of fuel is admitted to theelectric furnace somewhat above the top of the charge by means of thescrew conveyor 22. This fuel containing carbon drops on the hot chargein the furnace and assists in reducing the iron ore to iron. The fueladmitted by means of the screw conveyor 22 gives off a large volume ofgas when it drops on the top 'ofthe hot charge of the electric furnaceand this gas passes upwardly into the pipe 27 where it meets a supply ofair admitted through the air duct 51 and the tuyeres 52. At this point apartial combustion of the gas takes place, the completeness of saidcombustion bein regulated by the quantity of the air supplied throughthe air duct-51, so that the hottest zone in the reducing'furnace islocated at its lower end, and the temperature gradually diminishes asthe upper end is reached. The carbon contained in the charging mixturepassing through the furnace 28 is heated to a high temperature by thehot gases from the electric furnace, so that the carbon contained insaid fuel partly reduces the ore contained in the charging mixture. If aquantity of air insufficient forcomplete combustion is admitted to theair duct 51, carbon monoxideis formed, which also acts as a reducingagent in bringing the reductionof the iron ore nearer completion at thelower and the hotter end of the furnace 28, before said charging mixturedrops into the electric furnace. The hot gases passing through therotary furnace 28 also serve to decompose the lime stone usuallycontained in the charging mixture to form calcium oxideand carbondioxide. The gases are greatly cooled as they travel up the furmade 28until when near theupper end where .on by the waste gases from thefurnace before thecharging mixture reaches the electric furnace, so thatthe quantity of power ordinarily needed to carry out these reactions isgreatly diminished, and as a result about half the, electrical energyisneeded for each ton of iron smelted from its ore.

While my improved electric furnace is specially adapted'for the smeltingof iron from its ore, it may also be modified or adapted for the makingof any alloy such as ferro-chrome, cupro-vanadium, cupro-manganese,ferro-vanadium, ferro-molybdenum.

also calthe rotary furnace carry out chemical reactions which wouldotherwise have to be carried out at the expense of electrical energy, sothat as a result the furnace has a capacity per K. W. hour which isdouble that of the ordinary electric reduction furnace. Furthermore, ahigherfvoltage may be used and the waste gases going up the stack have avery low temperature so that the heat lost in the rocess is reduced to aminimum.

The reducing conditions obtained in the stack of an ordinary blastfurnace where the ore is partly reduced before reaching the hot zone, isexactly reproduced in m improved furnace on a still higher efliciency,as the charging material is continuously stirred by the rotary furnacewhile being subjected to the reducing gases passing therethrough.

In the use of an ordinary blast furnace it is absolutely essential touse a high grade metallurgical coke or anthracite coal, both of whichare very expensive, so that the charge will be porous enough for theuniform. distribution of the incoming blast of air. In my improvedelectric furnace any type of lou grade fuel may be used such as slackcoal, oil residue, etc. In many parts of the country large quantities offinely powdered coal and slack are thrown away because of the lack ofuses for the same. My improved furnace can be used in districts.containing available water power, and only a poor quality fuel unsuitedfor the production of coke, where it would be commercially impossible tooperate ablast furnace for thesmelting of the iron ore when the cokeessential for its operation would have to be shipped from a distance. Itis commonly known that the initial cost of installing an electricfurnace and the cost for repairs is much smaller than for a blastfurnace-for a given output, and my improved furnace embodies all ofthese qualities inherent in ordinary electric furnaces. This saving inthe cost of installation is specially noticed owing to the fact that amuch smaller quantity. of'

air is necessary in the'operation and therefore a much smaller unit ofblowing engines is necessary.

Many of the electric furnaces in use at present operate intermittently,and as a result a uniform product cannot be obtric current, and cut downthe output .of

the furnace until it is eventually necessary to shut it down; In theimproved furnace these conditions cannot occur and the loss of time dueto shut-downs will bereducedto a minimum.-

Another distinctive feature of this electric furnace, is that morecarbon may be used than is. necessary to just reduce the ore, since anexcess of carbon will not in jure the furnace as it does the ordinaryelectric reduction furnace. Furthermore the burdening of the furnacedoes not have to be so scientifically exact as in the ordinary electricreduction furnace, thus making it easier to operate said furnace andobtain results. In the improved furnace the composition of the charge iseasily controlled and a high silicon, high carbon, pig iron, or a lowsilicon, low carbon iron can be made which may be quickly converted intosteel in an electric steel furnace at an 'expenditure of 200 to 300 K.W. hours per ton. In operation the furnace. is very flexible since thequantity of air and pro-v portions of charge entering the furnacemay bevaried at the operators option, so that the furnace is easily adaptablefor the making of alloys of all descriptions, and the condition of thecharge during the operation. may be easily observed through thetransparent door. Since my improved furnace is charged automatically,the cost of labor in operating the furnace is greatly reduced over thatof the ordinary electrical furnace or the blast furnace.

It has been found that under certain conditions in a blast furnace thenitrogen in the air produces nitrides of iron, which have a bad effecton iron and steel since it renders them brittle. Consequently theelimination of nitrogen in the electric furnace not only preventsinefliciency but also allows certain grades of ore to be handled whichwould not submit to the usual treat ment by the blast furnace. This isparticularly important where magnetites occur which contain too muchsulfur for blast furnace treatment, butcan be economically smelted byuse of the electric current.

I would state in conclusion that while the illustrated exampleconstitutes a practical embodiment of my invention, I do not limitmyself strictly to the mechanical details herein illustrated, sincemanifestly the same can be considerably varied without departure fromthe spirit of the invention as defined in the appended claims.

Having thus described -my invention, 1 claim as new and desire to secureby Letters Patent:

1. The combination with an electric fur nace of a gas outlet in the roofof saidfurnace, means for injecting air into said outlet, a rotatablymounted tube connected to said outlet, said tube being positioned withits axis at an angle to the horizontal, a screw conveyor rotatablymounted in the upper end of said tube, a container associated with saidscrew conveyor, means for rotating said screw conveyor so as to transfercharging material from said container to the upper end of said tube, andmeans for rotating said tube so that said charging material will bedelivered to said electric furnace.

2. The combination with an electric furnace of a gas outlet in the roofof said furnace, means for injecting air into said outlet, a rotatablymounted tube connected to said outlet, said tube being positioned withits axis at an angle to the horizontal, means for supplying chargingmaterial to the up per end of said tube, means for rotating said tube sothat the charging material will be delivered to said electric furnace, acontainer, and a screw conveyor adapted to remove other charging fromsaid container and deliver it to said electric furnace.

3. The combination with an electric furnace of a gas outlet in the roofof said furnace, means for injecting air into said outlet, a rotatablymounted tube connected to said outlet, said tube being positioned withits axis at an angle to the horizontal, a rotatably'mountedscrewconveyor, a container associated with said screw conveyor, means forrotating said screw conveyor so as to transfer charging material fromsaid container to the upper end of said tube, means for rotating saidtube so that said charging material will be delivered to said electricfurnace, an auxiliary container, and a screw conveyor adapted to removeother charging material from the auxiliary container and deliver it tosaid electric furnace.

4. The combination with an electric furnace of a rotatably mounted tubepositioned with its axis inclined at an angle to the horizontal, thelower end of said tube being connected to an opening in said furnace,means for rotating said tube, and auxiliary means for continuouslyinjecting charging materials into said electric furnace.

5. The combination with an electric furnace of a gas outlet in the roofof said furnace, means for injecting air into said outlet, a rotatablymounted tube connected with said outlet, said tube being positioned withits axis at an angle to the horizontal, means for rotating said tube,means for introducing charging materials into the upper end of saidtube, and auxiliary means for introducing charging materials into saidfurnace.

6. The combination with an electric furnace of a gas outlet in the roofof said furnace, means for continuously injecting air into said outlet,a rotatably mounted tube connected with said outlet, said tube beingpositioned with its axis at an angle to the horizontal, means forrotating said tube, means for continuously introducing chargingmaterials into the upper end of said tube, and auxiliary means forcontinuously introducing charging materials into said furnace.

ROY A. DRISCOLL.

